Development of commercially acceptable formulations of the nematophagous fungus Verticillium chlamydosporium

Abstract

Studies in shaken flasks and a 20-liter bioreactor showed that biomass ofVerticillium chlamydosporiumcould be produced in large quantities in liquid culture. The fungus grew readily in media containing commercially available, low-cost ingredients (e.g., cotton seed meal, soybean meal) and a volumetric productivity of about 0.3 g/h/liter was achieved in the bioreactor. Chlamydospores were not produced in submerged culture, the biomass consisting only of mycelia and conidia. When this biomass was mixed with a carrier (kaolin) and a binder (gum arabic) and the ingredients were granulated and then dried to a moisture content of less than 2%, a biologically active product suitable for application to soil was produced. The fungus grew vigorously from these granules when they were placed on agar and retained its viability when granules were stored in vacuum-sealed bags at 25°C for 12 months. Experiments on tomato in the glasshouse showed that when the formulated product was incorporated into field soil at 10 g granules/liter soil, population densities ofV. chlamydosporiumwere increased to about 104colony-forming units/g soil after 7–14 weeks. Between 37 and 82% of the first generation egg masses produced byMeloidogyne javanicacontained parasitized eggs.